The potential effects of
Sources of copper in the marine
The effects of copper in the marine
Boats spend a large proportion of their working
life partly submerged in water. As with all objects subjected
to long periods of time in the water, boat hulls become prone
to colonisation by the many micro-organisms which inhabit the
aquatic environment. This colonisation is known as fouling.
The extent of infestation depends on a number of factors including
water temperature, salinity and productivity of the organic
matter on which the organisms feed.
Boat hulls are susceptible to all types of
fouling irrespective of the material from which they are constructed.
The fouling, if not attended to, causes increased drag on the
hull, leading to increased fuel consumption, and can eventually
cause significant damage to the boat structure. A heavily fouled
vessel may also lose manoeuvrability. It is, therefore, necessary
to apply some form of coating which will protect the hull against
infestation. These coatings are generally known as antifouling
paints and they are applied to the hull at regular intervals.
Antifouling paints usually contain a biocide,
or toxin, held within the structure of the paint. The coating
is designed to leach biocide slowly into the marine environment,
preventing any organism adhering to the paint by poisoning the
The nature of a biocide is such that potentially
it can have harmful effects, not only on the fouling organism
it is designed to deter, but also on other marine life unconnected
with fouling activity. It is the potential impact of these paints
on marine life that is the subject of this section.
For many years tributyltin (TBT) was the favoured
biocide for use in antifouling paints, although it was usually
used in conjunction with other biocides such as copper. However,
it became evident in the 1980s that its continued use was causing
severe damage to shellfish communities and, in particular, dog
whelk populations. This resulted in the implementation, in 1987,
of a Europe-wide ban on the use of TBT in antifouling paints
on boats under 25 meters. Its use is still permitted on craft
over this length and in certain industrial and agricultural
Before the widespread use of TBT, antifouling
paints were commonly based on copper. The ban on TBT resulted
in a shift back to paints which contain copper as the main biocide.
Copper is included in antifouling paints most commonly as cuprous
oxide, but also as cuprous thiocyanate and metallic copper powder.
One of the main drawbacks of the return to predominantly copper
based antifouling paints is that the copolymer type of paint,
which was initially developed for use with TBT, is not as effective
when used with copper biocides alone. Other drawbacks include
its incompatibility with aluminium hulled craft and the relatively
subdued colours that can be produced.
However, it is widely felt that although the
performance of copper biocides cannot approach that of TBT,
they remain the most effective of the alternatives for the foreseeable
future. To achieve as high a performance as possible from current
antifouling products, a 'booster' biocide is normally used as
copper is not fully effective against all fouling species.
There is currently a great deal of research
into alternative forms of biocides, particularly those of organic
origin. These, however, tend to be less universally effective
than other biocides and, in particular, may deter only specific
types of fouling organism. As a result of these 'species-specific'
characteristics, such biocides will almost always be used with
other biocides, including copper. The organic biocides are also
very expensive to develop and register. They are therefore usually
developed and registered in other industries first, such as
the agrochemicals industry, for use in other applications. Furthermore,
although they are from organic sources there is no assumption
that they are inherently less environmentally harmful than any
Teflon based antifouling paint is also available,
and has been used on racing yachts for a number of years. It
is particularly suitable for racing due to its low friction
surface, although it is not considered a particularly effective
antifouling coating when used without a biocide. There has been
some research into the use of silicon but this is at a fairly
early stage and as silicon is rather soft it is not an easy
material with which to work.
Antifouling paints utilising some form of copper
biocide account for over 95% of the total antifouling market
in the UK (personal communications) and this market share is
likely to persist for a considerable time. It is on these antifoulants,
therefore, that this section concentrates. This does not, however,
imply that the other biocides are necessarily any more or less
harmful, although there is little evidence available on their
Sources of Copper in the
Copper is a naturally occurring element and
is essential as a trace element for metabolic processes in living
organisms. However, it can also prove extremely toxic in high
concentrations. Therefore if copper accumulates to a significant
degree in the aquatic environment it can have a detrimental
effect on marine life.
Copper is present in all human and animal wastes,
and non-human activity, such as natural weathering, also leads
to copper input into the environment. However, the major sources
of copper contamination in inland and coastal waters are industrial
wastewater discharges and atmospheric deposition, particularly
from foundries and metal plating and cleaning operations. Fungicides,
wood preservatives and boat antifouling paints can also contribute
to high levels of copper in the aquatic ecosystem.
The Effects of Copper in
the Marine Environment
Due to its complex nature and the uncertainty
over its level of interaction with other substances, it is difficult
to establish the precise effect of elevated levels of copper
in the marine environment. Furthermore, although it may be possible
to detect the presence of copper concentrations in sediments
by sampling, it is rather more difficult to identify the source
of such concentrations. Depending on the location, sediments
can be highly mobile and resuspension of copper in the water
column can result in the transportation of the metal to areas
away from the main sources.
Therefore, before assumptions can be made concerning
the impact of copper-based antifoulant on the marine environment,
it is vital that further research is carried out. This should
be focused on identifying the sources of elevated levels of
copper found in the marine environment and establishing the
exact nature of any subsequent environmental impact.
In 1984, a UK government commissioned report
on copper, concluded that due to problems of quantifying the
exact environmental effect of differing copper concentrations,
it is difficult to generalise about the toxicity of copper to
marine organisms. There is, however, evidence to show that certain
species of fish and other marine organisms are sensitive to
quite low levels of copper even though other species are relatively
tolerant of much higher levels. Marine invertebrates are thought
to be slightly more sensitive to copper than fish. Furthermore,
evidence suggests that marine organisms have some capacity for
adaptation to higher than normal levels of copper although sudden
high inputs of the metal are likely to cause adverse effects
in otherwise unexposed populations.
Significant copper accumulation is unlikely
to occur in fast flushing open coastal areas, but can accumulate
in the sediments of low flushing waters including streams, rivers
and bays. The US National Oceanic and Atmospheric Administration
found that between the late 1970s and 1990, levels of copper
in marine organisms have steadily increased (World Resources
1992-93). This is an indication of increasing copper concentrations
in the aquatic environment.
There are relatively few studies that specifically
relate to the effect of copper based antifouling paints on the
marine environment and none which examine the potential impact
on the mSAC designated features. Those that do exist point to
evidence of elevated levels of copper in the vicinity of shipyards
and dry docks, whilst others found that marine organisms in
the vicinity of a marina had higher levels of copper than those
in an adjacent undeveloped bay.
The only research identified which specifically
assesses the concentrations of copper in the vicinity of marinas
is an undergraduate research project carried out at the University
of Southampton (Newbold, 1993). This involved sampling sediment
from several sites around Southampton Water to determine whether
marina environments were associated with elevated concentrations
of copper. The research found some evidence that copper based
antifouling paints have an effect on copper concentrations on
the surface sediment in the vicinity of the marinas sampled.
However, due to the mobility of copper in the water column,
it concluded that more research was required to determine whether
the effluent from industrial processes in the area is contributing
to such concentrations.
Some studies have been carried out into the
effects of particular substances contained within copper-based
antifoulants. For example, research into Ingarol 1051, a trizine
herbicide used to boost the effectiveness of antifoulant paints,
has suggested that it can result in reduced plant growth and
a reduction in photosynthesis.
Some European countries including Denmark have
now banned the use of certain biocides in antifouling paints.
The bans have been based on evidence that such substances do
indeed have a negative impact on the marine environment. However,
this evidence is disputed by industry and other EU countries
have been slow to follow suit.